Carrying a dangerous amount of weight has caused more deaths in England and Scotland than smoking since 2014, research suggests.
Being overweight or obese has been linked to numerous health conditions, including type 2 diabetes, heart disease and certain cancers.
To better understand its impact on mortality, scientists from the University of Glasgow analysed more than 192,000 adults in England and Scotland over 14 years.
Results suggest deaths that could be attributed to obesity or an excessive body weight increased from 17.9% in 2003 to 23.1% in 2017. This is compared to a reduced mortality-effect for smoking, from 23.1% to 19.4%.
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The scientists estimate the number of deaths that have come down to an individual's dangerously-high weight has exceeded those caused by smoking since 2014.
This comes after a University of College London study found a third of obese people who took a "game changing" drug lost more than a fifth of their body weight.
In 2004, the World Health Orgaization ranked smoking as the top risk factor for ill health in high-income countries, holding it responsible for nearly a fifth (18%) of all deaths, the Glasgow scientists wrote in the journal BMC Public Health.
At the time, obesity or excess weight was the third biggest risk factor, causing 8% of fatalities.
"For several decades, smoking has been a major target of public health interventions as it is a leading cause of avoidable deaths," said study author Professor Jill Pell.
"As a result, the prevalence of smoking has fallen in the United Kingdom.
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"At the same time, the prevalence of obesity has increased.
"Our research indicates that, since 2014, obesity and excess body fat may have contributed to more deaths in England and Scotland than smoking."
Smoking is the "largest contributor to cancers overall", however, a high body mass index (BMI) "exceeds" tobacco when it comes to tumours of the bowel, kidneys, ovaries and liver.
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The Glasgow scientists analysed the results of health surveys completed by thousands of people, with an average age of 50.
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The participants reported whether they had ever regularly smoked, while trained interviewers or nurses measured their height and weight.
This information was compared against nearly 200 studies that calculated the effects of obesity or excess weight on a person's premature death risk, as well as 17 research papers measuring the same for smoking.
The results suggest smoking-related deaths have declined, only to be overtaken by those linked to a dangerously-high BMI.
A difference was found across the participants' ages, however.
Among those aged 45 to 64, obesity or excess body weight was behind an estimated 3.4% more deaths than smoking in 2017, rising to 3.5% for people aged 65 or over.
Smoking, however, accounted for 2.4% more fatalities than a high BMI for the participants aged 16 to 44.
A person's sex may also play a role.
The results suggest obesity or excess body weight accounted for 5.2% more deaths than smoking among men in 2017, compared to 2.2% more deaths in women.
Deaths due to obesity or excess body weight are thought to have increased by 25.9% for women and 31% for men between 2003 and 2017, while smoking-related fatalities have fallen by 18.1% for females and 14.9% for males.
The scientists stressed their results are based on estimates, with further research being required. This could look at the effects of vaping, e-cigarettes and passive smoking; as well as if obesity-related deaths differ between ethnicities.
Ahead of further investigations, Professor Pell said: "The increase in estimated deaths due to obesity and excess body fat is likely to be due to their contributions to cancer and cardiovascular disease.
"Our findings suggest the public health and policy interventions aimed at reducing the prevalence of smoking have been successful.
"National strategies to address obesity and excess body fat, particularly focusing on middle-aged and older age groups and men, should be a public health priority."
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